I had some plants that looked a lot like this when their roots rotted off. How do your roots look? Other than that, the burt edges and upwards curling makes me think over fertilization. I used to run 1000-1200 PPM in my E&F system and was fine but have found that if I go over 800 in DWC, they get burned up really quickly. I also had to switch to RO water from my 350 PPM tap water and have had nothing but success so far, other than some new slight yellowing, so I really don't think its the water. How much CalMag are you using? I use CalMax which is basically the exact same thing except it has a little bit of nitrogen, and I use 1 tsp per gallon. Hopefully you get this figured out, those ladies look pretty rough.